1. Field of the Invention
The present invention relates to window frame assemblies, and in particular, to an assembly having a sliding glass mechanism and seal system for vehicular backlites. The assembly includes a frame for mounting the assembly in a vehicle, a pair of fixed side window panes secured in the frame, and one or more sliding window panes slidingly positioned between the fixed window panes.
2. Summary of Related Art
Pickup trucks and other related vehicles have a rear window, or backlite, that is mounted in an opening in the body panel immediately behind the seats in the passenger compartment. The backlites are supplied to the pickup truck manufactures as window frame assemblies for installation on the assembly line. The backlite assemblies typically include a metal frame, such as aluminum, provided with a top and bottom channels to facilitate the sliding of the glass panels.
The backlite assembly is mounted directly into the window opening in the body panel. The assembly is secured to the body panel with adhesives and/or mechanical fastener devices. A urethane adhesive is frequently used in the backlite applications, such adhesive being applied to the mounting surface of either the opening in the body panel or the backlite assembly prior to the moment at which these two structures are brought into abutment.
The backlite assembly in a pickup truck can be a source of problems, such as water leakage. The leakage may occur at the engagement of the backlite assembly and the body panel, which is typically caused by improper adhesive application or frame distortion. Water leakage may also occur around the seal extending about the four edges of the aperture in a sliding window. Two edges of the aperture are formed by the top and bottom channel. The other two edges are formed the internal edges of the fixed, side windows (or a pillar mounted thereon). A tight seal is required on all four edges of the sliding window to ensure the integrity of the seal.
The primary configuration currently used in the backlite assemblies consists of an assembly having a metal bracket with two channels extending around the complete perimeter of the assembly. The two fixed windows are mounted in an outer channel in planar, spaced-apart relationship with two horizontal and two vertical seals secured in the outer channel surrounding the opening between the fixed windows. The sliding window is disposed in the inner channel, adjacent the fixed windows. In the closed position, the sliding window sealably engages the seals to seal the opening between the fixed windows. When moved to an open position, the sliding window slides in the internal channel to overlap one of the fixed windows in the outer channel.
The seals are made from rubber or other equivalent material and include an extended lip which flexibly engages the sliding window to prevent water and dirt from entering around the sliding window. The rubber seals are mounted in the outer channel between the two fixed windows. The rubber seals facilitate the sliding of the sliding window in a horizontal direction while maintaining sufficient pressure at the lip of the seal to prevent water from leaking around the seal to the interior of the assembly and the pickup truck.
The rubber seals require a manual production step to properly install the seals around the opening of the assembly. One of the needs of the window manufacturers is to find an alternative sealing system which seals the opening without discrete rubber seals, thereby reducing material and labor costs during production operations and while improving the integrity of the seal around the sliding window.
Although rubber seals are expensive and difficult to install, such rubber seals may still be required or preferred in certain embodiments. If the rubber seals are not installed properly, then water leakage may occur in the horizontal channels or along the vertical edges of the aperture. An improved method, such as encapsulation, for securing the rubber seal about the aperture in the backlite is also desired in the industry.
In addition to the sealing problem noted above, there are several additional performance requirements which often present problems in the use of the sliding window assemblies in pickup trucks. In the closed position, the backlite window assembly must maintain the wind and road noise within acceptable limits. The seal must uniformly seal the sliding window to eliminate outside noise. The channel drain holes and other design features must be designed to eliminate road noise problems.
High or variable sliding force is another concern in backlite window assemblies. The sliding window typically includes rubber or plastic guides to secure the slidable window within the bottom internal channel. The slidable window should slide freely within the guides while still being positioned to sealably engage the lip of the rubber sealing member. If the seals are installed improperly, such as misalignment, then the sliding window may difficult to slide. The channels of the frame may also be misaligned. The sliding characteristics of the rubber seals and the channel guides should permit the sliding of the sliding window while maintaining the necessary seal force between the sliding window and the seal.
Another problem which frequently occurs with backlite assemblies is a sliding glass rattle. When the sliding glass is moved to an open position, the sliding glass in the internal channel must be retained by channel guides in order to prevent a rattle of the glass.
In summary, a backlite assembly with one or two sliding windows must maintain a proper seal to eliminate water leaks and wind/road noise in a closed position. The slidable windows, without compromising the required seal, must be easy to slide to facilitate the opening and closing of the backlite sliding window. In the open position, the sliding window must be secured in the channel to prevent a rattle of the glass.
In a backlite assembly, the required features include a tight seal and, conversely, easy sliding movement. Adhesives are used to secure the backlite assembly in the pickup truck and to secure the rubber seals and the guides in the assembly. Slip coats and other lubricants are often used to facilitate the sliding of the sliding glass against the seal and the guide walls. Applying adhesives and lubricants in such proximity on the same assembly adds to the production costs and could cause quality problems if either is applied improperly.
A window frame assembly for pickup truck backlites is disclosed in U.S. Pat. No. 5,294,168 to Kronbetter. The Kronbetter window assembly includes a complex top and bottom rail with two channels, an outer channel for mounting the two outer pieces of fixed glass and the rubber sealing members, and an inner channel for securing the guides and the sliding windows.
In Kronbetter, the assembly of the window frame starts with the insertion of the guides into the inner channels. Adhesive is applied to the outer channel to secure the fixed window panes in the frame. The sliding window panes are inserted into the guides and the bottom metal frame segment and the bowed, top metal frame segment are welded or otherwise bonded together. The sealing members are then placed in the outer channel of the frame to slidably and sealably engage the sliding windows in the inner channel. The window frame assembly is then ready for installation into a pickup truck.
The metal frame of the window assembly in Kronbetter is expensive to manufacture and assemble. Pickup truck manufacturers desire a less expensive window assembly that is easier to mount and still meets all of the performance requirements.
In recent years, motor vehicle glass suppliers have been supplying to motor vehicle manufactures, modular windows having urethane gaskets molded in situ by means of a reaction injection molding (RIM) encapsulation process. These gaskets encapsulate the peripheral edge of the glass window and provide an effective seal between the glass and the window opening in the metal automobile body. The gasket is formed by inserting a glass sheet in a suitable mold and injecting a liquid, plastic forming composition about the periphery thereof which polymerizes and cures in contact with the glass and tightly adheres thereto.
Prior to the development of the reaction injection molding process, vehicle window assemblies were comprised of a plurality of elements, including adhesive sealants applied around the marginal edges of the glass sheet, suitable mechanical fasteners such as metal clips, and exterior decorative trim strips disposed to cover the junction between the marginal edges of the glass sheet and the adjacent portion of the vehicle frame. These structures were costly in both material and labor, and were very difficult (if not impossible) to install using robotics. In order to install the windows using robotics, it was necessary that the windows have a gasket formed around the perimeter thereof.
The initial vehicular window gaskets were formed from a molded plastic material, such as polyvinyl chloride. The relatively high pressure required for the PVC injection molding process, however, resulted in glass breakage and other production related problems. The PVC window assembly process is described in U.S. Pat. No. 4,072,340 to Morgan.
In the 1980's, the reaction injection molding encapsulation process was developed to produce modular windows which would reduce glass breakage and facilitate the installation of motor vehicle windows by robots. U.S. Pat. No. 4,561,625 to Weaver describes the use of polyurethane molded on the peripheral edges of the glass at low pressures through the use of a RIM technique. The polyurethane gasket was of great significance since it eliminated the need for the conventional adhesive sealants, ancillary metal clips and exterior decorative trim strips disposed to cover the junction between the marginal edges of the glass sheet and the adjacent portions of the vehicle frame. The RIM encapsulated gasket worked better than the polyvinyl chloride gasket which was then being contemplated for use, in that the RIM method of forming the gasket permitted it to be done at lower pressures and accordingly substantially reduced the incidents of breakage of the glass.
U.S. Pat. No. 4,755,339 to Reilly et al. and U.S. Pat. No. 4,839,122 to Weaver disclose further details regarding the method and apparatus for reaction injection molding of window gaskets.
Metal brackets and spacers have been incorporated into the reaction injection molding process to improve the functionality of the glass. U.S. Pat. No. 4,662,113 to Weaver shows a window assembly used for door windows on motor vehicles which is operated in a vertical manner. A bracket is placed in the mold with the window glass and is integrally secured to the window glass during the formation of the gasket by the rim injection molding process. The bracket provides a means to connect a linkage or other drive means to the window glass to raise and lower the window in the motor vehicle.
U.S. Pat. No. 4,951,927 to Johnston et al. shows a spacer element used to maintain spacing between two sheets of glass. The spacer is positioned about the periphery of the sheets of glazed glass prior to positioning the glass in a mold for reaction injection molding to form an encapsulating gasket around the peripheral edge portions to produce a multiple glazed structure.
Because of the desirable features of the gaskets formed by reaction injection molding, the process has been used for several additional applications. U.S. Pat. No. 5,060,440 to Weaver discloses two glass sheets flexibly connected by adjacent gaskets joined during the reaction injection molding process. U.S. Pat. No. 4,996,808 to Weaver discloses an encapsulated window assembly in which a preformed sheet of plastic material is place in the mold prior to the gasket forming process.